Display system with low-latency pupil tracker

ABSTRACT

A display system aligns the location of its exit pupil with the location of a viewer&#39;s pupil by changing the location of the portion of a light source that outputs light. The light source may include an array of pixels that output light, thereby allowing an image to be displayed on the light source. The display system includes a camera that captures images of the eye and negatives of the images are displayed by the light source. In the negative image, the dark pupil of the eye is a bright spot which, when displayed by the light source, defines the exit pupil of the display system. The location of the pupil of the eye may be tracked by capturing the images of the eye, and the location of the exit pupil of the display system may be adjusted by displaying negatives of the captured images using the light source.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.16/978,440, filed Sep. 4, 2020, entitled DISPLAY SYSTEM WITH LOW-LATENCYPUPIL TRACKER, which is a 371 of International Application No.PCT/US2019/020376, filed Mar. 1, 2019, entitled DISPLAY SYSTEM WITHLOW-LATENCY PUPIL TRACKER, which claims the benefit of priority to U.S.Provisional Patent Application No. 62/638,607, filed Mar. 5, 2018,entitled DISPLAY SYSTEM WITH LOW-LATENCY PUPIL TRACKER, which is herebyincorporated by reference herein in its entirety.

INCORPORATION BY REFERENCE

This application incorporates by reference the entirety of each of thefollowing patent applications: U.S. application Ser. No. 14/555,585filed on Nov. 27, 2014, published on Jul. 23, 2015 as U.S. PublicationNo. 2015/0205126; U.S. application Ser. No. 14/690,401 filed on Apr. 18,2015, published on Oct. 22, 2015 as U.S. Publication No. 2015/0302652;U.S. application Ser. No. 14/212,961 filed on Mar. 14, 2014, now U.S.Pat. No. 9,417,452 issued on Aug. 16, 2016; U.S. application Ser. No.14/331,218 filed on Jul. 14, 2014, published on Oct. 29, 2015 as U.S.Publication No. 2015/0309263; U.S. application Ser. No. 15/789,895 filedon Oct. 20, 2017; U.S. patent application Ser. No. 15/442,461 filed onFeb. 24, 2017; U.S. Provisional Patent Application No. 62/474,419 filedon Mar. 21, 2017; U.S. application Ser. No. 15/271,802 filed on Sep. 21,2016, published as U.S. Publication No. 2017/0082858; and U.S.Publication No. 2015/0346495, published Dec. 3, 2015.

BACKGROUND Field

The present disclosure relates to display systems and, moreparticularly, to augmented and virtual reality display systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR”, scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the user. A mixed reality, or “MR”, scenariois a type of AR scenario and typically involves virtual objects that areintegrated into, and responsive to, the natural world. For example, inan MR scenario, AR image content may be blocked by or otherwise beperceived as interacting with objects in the real world.

Referring to FIG. 1 , an augmented reality scene 10 is depicted whereina user of an AR technology sees a real-world park-like setting 20featuring people, trees, buildings in the background, and a concreteplatform 30. In addition to these items, the user of the AR technologyalso perceives that he “sees” “virtual content” such as a robot statue40 standing upon the real-world platform 30, and a cartoon-like avatarcharacter 50 flying by which seems to be a personification of a bumblebee, even though these elements 40, 50 do not exist in the real world.Because the human visual perception system is complex, it is challengingto produce an AR technology that facilitates a comfortable,natural-feeling, rich presentation of virtual image elements amongstother virtual or real-world imagery elements.

Systems and methods disclosed herein address various challenges relatedto AR and VR technology.

SUMMARY

Some embodiments include a method for displaying images to a viewer. Themethod comprises providing a display device comprising a light sourceconfigured to display an image. The location of a pupil of an eye of theviewer is aligned with an exit pupil of the display device. Aligning theexit pupil and the pupil of the eye comprises capturing an image of aneye of the viewer; and displaying a negative image of the image of theeye on the light source. Light forming the negative image is modulatedto provide image content to the eye of the viewer.

Some other embodiments include a method for displaying images to aviewer. The method comprises providing a display device comprising alight source configured to output light, from a plurality of differentlight output locations, to an eye of the viewer. The location of an exitpupil of the display device is aligned with the position of a pupil ofthe eye of the viewer. Aligning comprises capturing an image of the eye;and selectively emitting light from one or more locations of the lightsource corresponding to a location of the pupil of the eye in the imageof the eye.

Yet other embodiments include a head-mounted display system comprisingan eye imaging device configured to capture images of an eye of a user.The display system also comprises a light source comprising a pluralityof selectively-activated light-emitting locations configured to emitlight to form a negative image of the eye. A spatial light modulator isconfigured to display image content to the user by encoding imageinformation in the light forming the negative image of the eye.

Additional examples of embodiments include:

EXAMPLE 1

A method for displaying images to a viewer, the method comprising:

-   -   providing a display device comprising a light source configured        to display an image;    -   aligning a location of a pupil of an eye of the viewer with an        exit pupil of the display device, wherein aligning the location        comprises:        -   capturing an image of an eye of the viewer; and        -   displaying a negative image of the image of the eye on the            light source; and    -   modulating light forming the negative image to provide image        content to the eye of the viewer.

Example 2

The method of Embodiment 1, wherein modulating light forming thenegative image comprises propagating the light through a spatial lightmodulator.

Example 3

The method of Embodiment 1, wherein the light source is a spatial lightmodulator, wherein the negative image is displayed on the spatial lightmodulator.

Example 4

The method of Embodiment 1, wherein the negative image of the eyedefines a location of an exit pupil of the display,

-   -   wherein aligning the location of the pupil of the eye is        performed continuously while providing image content to the eye,    -   wherein capturing the image of the eye and displaying the        negative of the image are performed 60 or more times per second.

Example 5

A method for displaying images to a viewer, the method comprising:

-   -   providing a display device comprising a light source configured        to output light, from a plurality of different light output        locations, to an eye of the viewer;    -   aligning a location of an exit pupil of the display device with        a position of a pupil of the eye of the viewer, where aligning        comprises:        -   capturing an image of the eye; and        -   selectively emitting light from one or more locations of the            light source corresponding to a location of the pupil of the            eye in the image of the eye.

Example 6

The method of embodiment 5, further comprising:

-   -   modulating the light emitted from the one or more locations; and    -   propagating the modulated light to the eye to provide image        content to the viewer.

Example 7

The method of Embodiment 5, wherein the light source comprises a spatiallight modulator.

Example 8

The method of Embodiment 5, further comprising converting the image ofthe eye into a negative image,

-   -   wherein selectively emitting light comprises displaying the        negative image on the light source.

Example 9

A head-mounted display system comprising:

-   -   an eye imaging device configured to capture images of an eye of        a user;    -   a light source comprising a plurality of selectively-activated        light-emitting locations configured to emit light to form a        negative image of the eye; and    -   a spatial light modulator configured to display image content to        the user by encoding image information in the light forming the        negative image of the eye.

Example 10

The display system of Embodiment 9, wherein the eye imaging devicecomprises a camera.

Example 11

The display system of Embodiment 9, wherein the light source is an otherspatial light modulator.

Example 12

The display system of Embodiment 11, wherein the other spatial lightmodulator is an emissive spatial light modulator.

Example 13

The display system of Embodiment 12, wherein the emissive spatial lightmodulator is an LED array.

Example 14

The display system of Embodiment 9, further comprising:

-   -   light source optics configured to collimate light propagating        from the light source to the spatial light modulator;    -   light source relay optics configured to receive light from the        spatial light modulator and to form an image of the light        source; and    -   pupil relay optics configured to receive light from the light        source relay optics and to provide simultaneous images of the        light source and spatial light modulator to the eye.

Example 15

The display system of Embodiment 9, further comprising a light guideconfigured to direct light from the spatial light modulator towards aneye of the user.

Example 16

The display system of Embodiment 15, wherein the light guide has opticalpower and is configured to output light with a divergent wavefront.

Example 17

The display system of Embodiment 16, further comprising a plurality ofthe light guides, wherein at least some of the plurality of light guideshave different optical power from others of the plurality of lightguides.

Example 18

The display system of Embodiment 9, further comprising a frameconfigured to mount on a head of the user,

-   -   wherein at least a light capturing portion of the eye imaging        device is attached to the frame, and    -   wherein the spatial light modulator is attached to the frame.

Example 19

The display system of Embodiment 9, wherein the display system isconfigured to threshold the captured images of the eye to convert acaptured image to a corresponding negative image.

Example 20

The display system of Embodiment 9, wherein the light source is a binaryspatial light modulator, wherein the selectively-activatedlight-emitting locations have an on state and an off state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2A illustrates an example of a display system having a light sourcehaving a single light emitter.

FIG. 2B illustrates an example of a display system having a light sourcewith multiple light emitters which emit light from different locations.

FIG. 3 illustrates an example of a display system having a camera forcapturing images of a viewer's eye and a light source configured todisplay a negative of the captured image.

FIG. 4 illustrates an example of the exit pupil of the display system ofFIG. 3 tracking movement of the viewer's eye.

FIG. 5 illustrates an example of a display system with an opticalcombiner.

FIG. 6 illustrates an example of the display system of FIG. 5 having anoff-axis, mirror based eye imaging device.

FIG. 7 illustrates an example of a display system with a folded relaymirror combiner.

FIG. 8 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIGS. 9A-9C illustrate relationships between radius of curvature andfocal radius.

FIG. 10 illustrates a representation of the accommodation-vergenceresponse of the human visual system.

FIG. 11 illustrates examples of different accommodative states andvergence states of a pair of eyes of the user.

FIG. 12A illustrates an example of a representation of a top-down viewof a user viewing content via a display system.

FIG. 12B illustrates another example of a representation of a top-downview of a user viewing content via a display system.

FIG. 13 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence.

FIG. 14 illustrates an example of a light guide stack for outputtingimage information to a user.

FIG. 15 illustrates an example of a stacked light guide assembly inwhich each depth plane includes images formed using multiple differentcomponent colors.

FIG. 16 illustrates a cross-sectional side view of an example of a setof stacked light guides that each includes an incoupling opticalelement.

FIG. 17 illustrates an example of wearable display system.

DETAILED DESCRIPTION

Virtual and augmented reality near-eye display systems, including mixedreality display systems, preferably are able to provide imageinformation to the eye of a viewer with high optical quality, while alsoallowing continuous reception of that image information as the viewer'seye moves. For example, the user is preferably able to continue toreceive image information (e.g., to view displayed images) even whentheir eyes move relative to the display. The image information may takethe form of modulated light from a light source. For example, light froma light source may be may be modulated by a spatial light modulator toencode the light with the image information before directing themodulated light into the eye of the viewer. To form a compact and/orportable display system, the display system preferably efficientlyutilizes the light from the light source. High efficiency reduces thepower requirements of the light source while still producing a desirablybright image. The more efficient the light utilization, the smaller andlonger-operating the display system may generally be.

It will be appreciated that modulated light may be provided to theviewer's eye through an exit pupil of the display system. For example,the display system may utilize a projection/relay system that transfersimage light from the spatial light modulator to an infinity ornear-infinity focused image that is viewed by the viewer through an exitpupil formed by an upstream projector optical system. In these opticalsystems, the exit pupil of the system may be small (e.g., 0.5-2 mm),which may require careful alignment of the viewer's ocular pupil (thepupil of an eye of the viewer) with the exit pupil, to preferably allowall of the light exiting the display system to enter the ocular pupil.Misalignments of the exit pupil and the ocular pupil can cause some ofthe light exiting the display system to not be captured by the viewer'seye, which may cause undesirable optical artifacts, such as vignetting.

Pupil expansion may be employed in the display system to relax alignmentrequirements. For example, a pupil-expanding eyepiece may be used todiffractively sample input light into a plurality of beamlets across aneyepiece, which may be formed by one or more light guides. For example,pupil expansion may involve replicating rays of light across theeyepiece. An “eye-box” may be described as an area or volume in whichthe viewer places his/her pupil in order to see the image formed usingthe spatial light modulator, e.g., by capturing the beamlets exiting theeyepiece. The large size of the eyebox allows the viewer's pupil to moveand rotate without the viewer perceiving significant vignetting. This,however, is achieved at the cost of efficient light utilization, sincethe viewer's eye will only sample a small percentage of the lightpresent in the eyebox at a given instant in time. Thus, much of thelight emitted by the light source and later outputted by the eyepiecedoes not enter the ocular pupil of the viewer.

The optical elements used to replicate and output rays of light from alight guide of an eyepiece may also contribute to the inefficient lightutilization. For example, the use of diffractive structures themselvesmay contribute to light utilization inefficiencies since the diffractivestructures typically do not direct all light in a single desireddirection, nor do diffractive structures typically uniformly directlight of different wavelengths in a desired direction. In addition, auniform distribution and flux of light out of the eyepiece is desirableto provide high perceived image quality, including high uniformity inimage brightness as the ocular pupil moves across the eye-box. In someconfigurations, the optical elements that out-couple light out of thelight guide may be diffractive structures with low diffractionefficiencies, in order to facilitate the uniform distribution of lightacross an eye-box and out of the eyepiece. Thus, similar to the above,only a small portion of the light coupled into a light guide from thelight source is outputted out of the light guide and into the ocularpupil at a given location across the light guide. In someconfigurations, the desire for uniformity may result in use ofdiffractive elements with diffraction efficiencies that are so low thatsome of the light coupled into the light guide is not outputted to theviewer before passing completely across the light guide.

Advantageously, in some embodiments, a display system provides highlyefficient light utilization using an exit pupil that tracks and alignswith the ocular pupil of the viewer. The alignment may be achieved usinga light source that comprises a plurality or an array ofselectively-activated light output locations. Changing the location atwhich light is outputted by the light source changes the laterallocation of the exit pupil, thereby allowing the exit pupil to be movedto track the ocular pupil.

In some embodiments, each of the selectively-activated light outputlocations of the light source may function as a pixel, and selectivelyactivating different ones of these light output locations may allow animage to be displayed by the light source. In addition to the lightsource, the display system may comprise an imaging device for capturingimages of the eye. The captured images are converted into negativeimages, which are displayed by the light source. In the negative images,the dark pupil of the eye appears as a bright spot which, when displayedby the light source, defines the exit pupil of the display system. Thus,the location of the ocular pupil may effectively be determined bycapturing images of the eye, and the location of the exit pupil of thedisplay system may be set by using the light source to display negativesof those captured images. In operation, in some embodiments, images ofthe viewer's eyes may be continuously captured and the displayednegatives of the captures images may similarly be updated continuously,thereby allowing the position of the exit pupil to be adjusted and tocontinuously track the position of the ocular pupil. In someembodiments, the light outputted by the light source may then bemodulated to encode image information before that light exits thedisplay system. It will be appreciated that for displays that displayimages to both eyes of a viewer, in some embodiments, the system maycomprise dedicated imaging devices, light sources, and related objectsfor each eye.

Advantageously, various embodiments of the display systems disclosedherein can provide a number of benefits. For example, the displaysystems may provide a highly efficient utilization of light. Because theexit pupil moves to track the location of the viewer's eyes, the displaysystem may not require pupil-expansion across a large area encompassingthe possible locations of the ocular pupil. Rather than attempting touniformly output light across a large eye-box, in some embodiments,substantially all of the light outputted by an emissive light source isavailable to be directed into the viewer's eyes, depending on anymodulation of that light to encode image information. In addition, thehigher light utilization efficiency can allow for a more compact deviceand longer run time with a given amount of stored power.

The ability to track and align the viewer's ocular pupil with the exitpupil may also improve image quality. For example, maintaining alignmentof the ocular in exit pupils may allow substantially all of the lightexiting the exit pupil to be captured by the viewer's eyes, therebydecreasing the occurrence of optical artifacts, e.g., vignetting. Theocular and exit pupil tracking and alignment also allows the use ofspecular optical relays to produce the exit pupil and may obviate theneed for leaky diffractive structures. This may obviate the difficultiesof diffractive structures in providing coherent light output. Inaddition, because only light for forming the single exit pupil isutilized to display an image, the amount of light propagating throughthe system is reduced, which may reduce the amount of unintentionallyscattered light reaching the viewer's eyes. This reduction inunintentionally scattered light can advantageously increase theperceived contrast of displayed images.

Various embodiments disclosed herein may also advantageously becompatible with a wide variety of optical combiners, as discussedherein. In addition, because the tracking and alignment of the exit andocular pupils principally involves relatively simple processes relatedto capturing, inverting, and displaying negative images of the eye, thetracking and alignment may advantageously be performed with low latencyand utilize low amounts of processing resources.

Reference will now be made to the drawings, in which like referencenumerals refer to like parts throughout. Unless indicated otherwise, thedrawings are schematic and not necessarily drawn to scale.

FIG. 2A illustrates an example of a display system having a light sourcewith a single light emitter. The display system includes a light source1000 having a light emitter 1002. The light emitter 1002 emits the lightthat will ultimately enter an ocular pupil 208 of an eye 210 of aviewer, to form images in that eye 210.

The display system may also include light source condensing/collimatingoptics 1010. The light source condensing/collimating optics 1010 may beconfigured to collimate light emitted by the light emitter 1002 beforethe light reaches an image spatial light modulator (SLM) 1020.

The image SLM 1020 is configured to modulate light from the light source1000. The image SLM 1020 may comprise an array of pixel elements, eachof which may modify light interacting with (e.g., incident on, orpropagating through) the pixel element. Images may be formed bymodulating the light (e.g., changing the intensity of the light,selectively transmitting light of certain wavelengths and/orpolarizations, etc.). As result, the image SLM 1020 may be said toencode the light with image information before the light reaches the eye210. It will be appreciated that the image SLM 1020 may be transmissiveor reflective. Where the image SLM 1020 is reflective, additionaloptical elements (e.g., a beam splitter and related optical elements)may be provided to direct the light from the light source 1000 to theimage SLM 1020 and towards the eye 210. Additional details regarding theuse of reflective spatial light modulators may be found in, e.g., U.S.patent application Ser. No. 15/442,461, filed on Feb. 24, 2017, theentire disclosure of which is incorporated by referenced herein. In someembodiments, the image SLM 1020 may take the form of a liquid crystaldisplay (LCD), including a liquid crystal on silicon (LCOS) display.

The display system may also include relay optics or lens structure 1030configured to produce an output or exit pupil, which is also an image1031 of the light emitter 1002. A viewer placing his/her ocular pupil208 at the location of the exit pupil (at the image 1031) would see aninfinity-focused image of the image SLM 1020. Such configurations may beutilized in virtual reality or other display systems in which the vieweris provided images directly from the system without, e.g., combining theimage content with other light, such as that from the ambientenvironment.

In some embodiments, a relay lens system 1040 may be provided in thepath of light between the relay optics 1030 and the ocular pupil 208 ofthe viewer. The relay lens system 1040 may be, e.g., a 4F relay system.In some embodiments, the relay lens system 1040 may be understood toschematically represent an eyepiece, e.g., a combiner eyepiece, examplesof which are discussed further herein. The combiner eyepieceadvantageously allows a view of the ambient environment by transmittinglight from this environment to one or both eyes of the viewer, whilealso allowing images outputted by the display system to be combined withthat light. Such a display system may constitute an augmented realitydisplay system.

With continued reference to FIG. 2A, as discussed above, the relayoptics 1030 may be configured to form the image 1031 of the lightemitter 1002, which may be between the relay optics 1030 and the relaylens system 1040. The relay lens system 1040 may include first andsecond lens 1042 and 1044, respectively. An image of the image SLM 1020may reside between the first lens 1042 and the second lens 1044 of therelay lens system 1040. A viewer placing his/her ocular pupil 208 at thelocation of the exit pupil (that is, at the image of the light emitter1002 provided by the relay lens system 1040) sees an infinity-focusedimage of the image SLM 1020.

In some embodiments, it may be desirable to focus the image of the SLM1020 on a plane other than infinity. For such embodiments, a lensstructure 1046 (e.g. a meniscus lens) may be provided in the path oflight between the output of the relay lens system 1040 and the viewer.The lens structure 1046 may modify the focus of the image of the SLM1020 at a desired depth plane. In some embodiments, the lens structure1046 may be omitted, e.g., where the second lens 1044 focuses the imageof the SLM 1020 at a desired depth plane. It will be appreciated thatthe first and second lens 1042 and 1044, in addition to other lensesdisclosed herein, may include one or more lens elements or groups oflens elements.

With continued reference to FIG. 2A, the location of the exit pupil maybe determined by the location of the light emitter 1002. Laterallydisplacing the light emitter 1002 correspondingly shifts the location ofthe exit pupil. For example, placing the light emitter 1002 at differentlocations causes the light from the light emitter 1002 to take differentpaths through the various optical structures of the display system(e.g., the condensing/collimating optics 1010, the relay optics 1030,and the relay lens system 1040). As a result, shifting the position ofthe light emitter 1002 can cause a corresponding shift in the locationof the exit pupil. A similar shift in the location of the exit pupil mayalso be achieved using one or more additional light emitters atdifferent locations; that is, rather than shifting the light emitter1002 to one or more other locations, other light emitters may beprovided at those locations.

FIG. 2B illustrates an example of a display system having a light sourcewith multiple light emitters which emit light from different locations.The display system of FIG. 2B is similar to the display system of FIG.2A except that the light source 1000 includes two light emitters, lightemitters 1002 and 1004, at different locations. In this illustration,light from light emitter 1002 is shown as dashed lines, and light fromlight emitter 1000 is shown as solid lines. The light sourcecondensing/collimating optics 1010 receives light from either lightemitter and condenses/collimates that light such that it propagates tothe image SLM 1020 as a collimated beam of light. However, because ofthe differences in location between light emitter 1000 and light emitter1004, the light from each light emitter propagates towards the image SLM1020 at different angles. As such, the relay optics 1030 forms images ofboth the light emitter 1002 and the light emitter 1004 between the relayoptics 1030 and the relay lens system 1040, but these images of lightemitters are offset from one another. In addition, images of the imageSLM 1020 formed by light from each of the light emitters 1002 and 1004may both reside between the first lens 1042 and the second lens 1044,with these images of the image SLM 1020 also being offset from oneanother. Depending on the spacing between the light emitters 1002 and1004, light form both exit pupils may simultaneously enter the viewer'seye 210, and the viewer may continue to see a single image of the SLM,focused at infinity. The differences in the locations of the lightemitters 1002 and 1004 provide exit pupils that are at differentlocations and the eye 210 may shift between the different exit pupilsand the image of the image SLM 1020 will continue to be visible as theeye 210 shifts. Advantageously, the addition of the second light emitter1004 may in effect expand the size of the exit pupil of the system.

In some embodiments, the light emitters 1002 and 1004 may be part of anarray of light emitters. For example, the light source 1000 may be aspatial light modulator. The spatial light modulator forming the lightsource 1000 may be an emissive spatial light modulator, e.g., comprisingpixels formed of light-emitting diodes (such as organic light-emittingdiodes (OLEDs)) which spatially modulate light by outputting light ofvarying intensities and/or wavelengths from pixels at differentlocations across an array of the pixels. In some other embodiments, thespatial light modulator may be a transmissive or reflective SLMconfigured to modulate light provided by illumination optics.

Where the light source is a spatial light modulator, individual pixels,or groups of pixels, of the spatial light modulator may constitute thelight emitters 1002 and 1004. As noted above, images of each of thelight emitters 1002 and 1004 may provide respective corresponding exitpupils for the display system, with the locations of the exit pupilsdetermined by the locations of the light emitters 1002 and 1004. Asdiscussed above, the locations of the light emitters may be shifted byselectively activating light emitters (the different pixels) atdifferent locations on the spatial light modulator. In addition, becausethe exit pupils are defined by images of the light emitters, the sizesof those light emitters also define the sizes of the exit pupils.Consequently, in some embodiments, the sizes and locations of the exitpupils may be set by selectively activating pixels of the spatial lightmodulator that forms the light source 1000.

For example, as discussed with reference to FIG. 2B, an image of thelight emitters (the light source SLM 1000 with its activated pixels inthis case) may be relayed through the display system. When the viewerplaces his/her eye 210 in the image of the SLM forming the light source,they will see an infinity-focused image of the image SLM 1020. The sizeof the exit pupil will be determined by the number of pixels that areactivated on the light source 1000's SLM, also referred to herein as thelight source SLM 1000. The position of the exit pupil may be determinedby which pixels on the light source SLM 1000 are activated. Thus, if asingle pixel on the light source SLM 1000 is activated, a single, smallexit pupil is formed at the viewer's eye when positioned in the image ofthe light source SLM 1000. If the single pixel is moved (that is, ifthat pixels deactivated and another single pixel at a different locationon the light source SLM 1000 is activated), the exit pupil of thedisplay system will correspondingly move. In all of these cases, theinfinity-focused image of the image SLM will preferably remainstationary within the exit pupil and be visible through the exit pupil,wherever it may be and however large or small it may be.

Advantageously, the ability to laterally change the location of the exitpupil can provide advantages for image quality and/or energy efficiency.For example, the display system may be configured to change the locationof the exit pupil so that it tracks the position of the ocular pupil.This may decrease the occurrence of optical artifacts, e.g., vignetting,and thereby increase perceived image quality and decrease unintendedfluctuations in image brightness. In addition, by continuously trackingand aligning the ocular and exit pupils, the display system may avoidthe use of low-efficiency diffractive optical elements. Moreover, wherethe light source comprises emissive light emitters (e.g., LEDs,including OLEDs), only those light emitters contributing light for theexit pupil may be activated at any given time. As a result,substantially all of the light emitted by the light source may becaptured by the viewer's eyes, thereby increasing the light utilizationefficiency of the display system.

In addition, utilizing a light source comprising a plurality ofindependently activated light emitters effectively allows the size ofthe light source to be changed, e.g., dynamically changed over thecourse of displaying images to the viewer. This changeability allows,e.g., the depth of field of the display system to be modified, e.g.,continuously modified while displaying images to the viewer. Forexample, the size of the light source may be increased by activating arelatively large number of light emitters, while the size of the lightsource may be decreased by activating a smaller number of light emitters(e.g., a single light emitter). A larger light source would be expectedto produce a shallow depth of field image of the SLM 1020, while arelatively small light source would be expected to produce a deep depthof field image of the SLM 1020. The ability to change the effective sizeof the light source may have advantages for managing the accommodativefunction of the viewer's eyes. For example, the sensitivity of theuser's eyes to accommodative cues may be set at a relatively high levelby utilizing a relatively large light source, while the sensitivity ofthe user's eyes to accommodative cues may be decreased by utilizing arelatively small light source. This may have advantages for, e.g.,reducing the impact of accommodation-vergence mismatches. For example,where the accommodation-vergence mismatch is expected to exceeddesirable threshold levels, the size of the light source may bedecreased to decrease the sensitivity of the user to the accommodativecues associated with the mismatch.

It will be appreciated that a light source comprising a plurality ofselectively-activated light emitters may be considered to functionroughly as a display. Where the light source is a spatial lightmodulator, the light source may indeed be considered to be a type ofdisplay device. In some embodiments, the ocular pupil may be tracked bycapturing images of the eye 210 of the viewer and displaying modifiedforms of those images on the light source SLM 1000. Because the ocularpupil is dark or black but the exit pupil should emit light, the displaysystem may be configured to display negatives of the captured images ofthe eye 210 on the light source SLM 1000. In the negatives, relativelydark pixels or areas of the captured images appear relatively light orbright, and relatively light or bright pixels or areas of the capturedimages appear relatively dark. As a result, the dark ocular pupil mayappear white or bright, while other areas of the eye 210 (such as thewhites of the eyes) are dark. Thus, light emitters corresponding to theocular pupil are activated (to emit light), while light emitterscorresponding to other areas of the eye 210 are not activated (to notemit light).

FIG. 3 illustrates an example of a display system having a camera forcapturing images of a viewer's eye and a light source configured todisplay a negative of the captured image. The light source 1000comprises a plurality of light emitters. For example, the light source1000 may be an SLM, which may comprise a panel display which may includein array of light emitters such as LEDs or lasers. The light source 1000displays a negative image of the viewer's eye 210. This negative imageprovides the exit pupil through which the image SLM 1020 is visible.

The display system includes an imaging device 1050 to capture images ofthe eye 210. In some embodiments, the imaging device 1050 may comprise adigital video camera and/or a digital still camera. In some embodiments,the imaging device 1050 may be configured to continuously capture imagesof the eye 210, or to capture such images at a desired rate. Forexample, the images may be captured and negatives of the images may bedisplayed at a sufficiently fast rate that updates to the negativeimages displayed by the light source SLM 1000 are not perceptible. Insome embodiments, the negative images are updated at a rate greater thanthe flicker fusion threshold, e.g., greater than 60 times per second (or60 Hz), our greater than 90 times per second (or 90 Hz).

With continued reference to FIG. 3 , the display system comprises aprocessing unit 1051 configured to receive captured images and toconvert those images into negative, preferably high contrast, images fordisplay by the light source SLM 1000. The processing unit 1051 is incommunication with the imaging device 1050 and receives a captured image1052 (e.g., in the form of data representing the captured image) of theeye 210 from the imaging device 1050. In some embodiments, the capturedimage 1052 is a grayscale or black and white image. The processing unit1051 includes an inverter 1060 configured to convert the captured image1052 into a negative of that captured image, thereby forming thenegative image 1062. For example, the normally black pupil now becomeswhite in the negative image 1062. The processing unit 1051 may beconfigured to then transmit the negative image 1062 (e.g., in the formof data representing the negative image) to the light source SLM 1000,which then displays the negative image 1062.

In some embodiments, the inverter 1060 may be configured to invert theintensity value of each pixel of the captured image 1052. As an example,for an 8-bit grayscale image having 256 grade levels and correspondingintensity values from 0-255, the inverter 1060 may be configured toinvert the intensity of a pixel by reversing the intensity values; thatis, an intensity value of X (X more than 0, the lower bound of possibleintensity values), may be inverted by converting that value to a numberthat is X less than 255 (the upper bound of possible intensity values).

In some other embodiments, the inverter 1060 may be configured toperform thresholding. For example, the inverter 1060 may be configuredto convert each “dark” pixel having an intensity less than a thresholdvalue to a pixel having a particular higher intensity (e.g., the maximumintensity). Preferably, the threshold value is set at a level such thatsubstantially only black pixels of the captured image 1052 representingthe ocular pupil 208 are converted to white pixels having in the higherintensity. In some other embodiments, the light source SLM may be abinary SLM with pixels configured to provide only two levels ofintensity (e.g., to provide only black and white, or on and off,states). The use of binary SLMs may obviate the need for thresholding.

In addition to inverting the captured image 1052 of the eye, in someembodiments, the processing unit 1051 may be configured to exclude, inthe negative image, dark portions of the captured image that are not theocular pupil 208. For example, the iris of the eye 210 may also includeblack portions. To exclude such parts of the iris from the negativeimage, the processing unit 1051 may be configured to perform imagerecognition and to determine, in real time, whether a pixel forms partof an image of the iris or whether the picture forms part of an image ofthe ocular pupil 208. In some embodiments, the processing unit 1051 maybe configured to identify a round area that is substantially entirelyblack as the ocular pupil 208 and to only show this round area (usingwhite pixels) in the negative image 1062.

In some embodiments, the processing unit 1051 may be part of the localprocessing and data module 140 and/or the remote processing module 150(FIG. 17 ). In some other embodiments, the local processing unit 1051may be part of the light source SLM 1000 itself. In such embodiments,transmitting the negative image 1062 for display by the light source SLM1000 may encompass simply transmitting image information betweencircuitry (e.g., inverter circuitry and display circuitry) within thelight source SLM 1000.

With continued reference to FIG. 3 , the negative image 1062 may bedisplayed by the light source SLM 1000. As discussed herein, images ofthe light source SLM 1000 and image SLM 1020 may be relayed through thedisplay system. For example, the relay optics 1030 forms images 1032 ofthe light source SLM 1000 between the relay optics 1030 and the relaylens system 1040. In addition, images of the image SLM 1020 are formedbetween the first lens 1042 and the second lens 1044 of the relay lenssystem 1040. The relay lens system 1040 also forms an image 1048 of thelight source SLM 1000. Placing the viewer's eye 210 in the light sourceSLM image 1048 allows the viewer to see an infinity-focused image of theimage SLM 1020.

Preferably, the exit pupil and the ocular pupil have substantially thesame size. For example, when the light source SLM 1020 is showing anegative image 1062, the size of the ocular pupil 208 reproduced in theimage 1048 of the negative image 1062 is substantially the same size asthe actual ocular pupil 208. It will be appreciated that the focallength of the lens of the camera 1050 and the size of the image sensorof that camera 1050 will determine the relative size of the ocular pupil208 within the captured image of that ocular pupil, and this relativesize may be different from the actual size of the ocular pupil 208.Thus, there is a scaling factor between the actual size of the ocularpupil 208 and the size of the ocular pupil 208 within the capturedimage. In addition, the various lens structures (e.g., the lenses 1010,1030, 1042, and 1044) between the light source SLM 1000 and the ocularpupil 208 may also have associated scaling factors. All of these scalingfactors may be taken into account to produce the image 1048 having animage of the ocular pupil 208 of a desired size at a location coincidingwith the pupil position 208. For example, the size of the negative imageof the ocular pupil 208 shown on the SLM 1000 may be increased ordecreased to provide the image 1048 having the ocular pupil 208 of adesired size.

In some other embodiments, the size of the group of activatedlight-emitting pixels on the light source SLM 1020 may provide an exitpupil that is smaller or larger than the size of the ocular pupil 208.For example, the intensity values for thresholding may be selected suchthat both the iris and the pupil of the eye 210 are shown as whitepixels in the negative image 1062. As a result, the size of the exitpupil may correspond to the size of the iris of the eye 210. In someother embodiments, as disclosed herein, the size of the light emittingarea on the light source SLM 1020 (e.g., the size of the negative of thepupil of the eye 210) may be modified to control the depth of focus ofthe display system.

It will be appreciated that the light source SLM image 1048 includes awhite spot which defines the exit pupil of the display system. Movementof the ocular pupil 208 with the eye 210 may be tracked by continuallycapturing new images 1052 of the eye 210. In addition, the alignment ofthe exit pupil of the display system with the ocular pupil 208 may becontinually updated (e.g., in real-time) by continually converting thecaptured images 1052 into negative images 1062 that are displayed on thespatial light modulator 1000. For example, as the ocular pupil 208shifts in position, this shift is captured in the captured image 1052which then causes a shift in the position of the high-intensity area ofthe negative image 1062. This updated negative image 1062 with theshifted high-intensity area is then displayed on the light source SLM1000, which causes the exit pupil to shift. As a result, changes inposition of the ocular pupil 208 cause corresponding changes in theposition of the exit pupil. Thus, the exit pupil may be understood totrack the position of the ocular pupil 208 substantially in real-time.

FIG. 4 illustrates an example of the exit pupil of the display system ofFIG. 3 tracking movement of the viewer's eye. An upward shift in theorientation of the eye 210 may be observed in an image captured by theimaging device 1050. To simplify the illustration, the captured imageand the resulting converted negative image are not shown. However, asdiscussed above regarding FIG. 3 , it will be understood that capturedimages are received by the processing unit 1051 and negatives of thosecaptured images are formed by the inverter 1060. The negative images areprovided to and displayed by the light source SLM 1000. Consequently,the upward shift in the orientation of the eye 210 causes acorresponding upward shift in the image of ocular pupil displayed by thelight source SLM 1000. The upward shift in the image of the ocular pupilcauses an upward shift in the exit pupil, thereby aligning the exitpupil with the ocular pupil 208.

It will be appreciated that augmented reality systems may utilizeoptical combiners that allow light from the ambient environment topropagate to the viewer's eyes to allow a view of the ambientenvironment, while also allowing light from a displayed image to alsopropagate to the user's eyes; that is, light from the ambientenvironment (the real world) and light containing image information fromthe display may be combined and both may be received by the viewer'seyes. In some embodiments, the optical combiner may be a light guide(e.g., a waveguide) that is at least partially transparent in thedirection of the viewer's gaze, thereby allowing for visibility of thereal world. The light guide may also be configured to guide light fromthe light source SLM 1000 and the image SLM 1020, encoded with imageinformation and output that light towards the viewer's eye 210. It willbe appreciated that light may be guided and propagate within the lightguide by total internal reflection. Also, throughout this disclosure, awaveguide may be understood to be an example of a light guide.

FIG. 5 illustrates an example of a display system with an opticalcombiner. The illustrated display system is similar to that shown inFIGS. 3 and 4 , except that the relay lens system 1040 is an opticalcombiner. As illustrated, the relay lens system 1040 includes a lightguide 1070 (e.g., a waveguide) and reflective lens structures 1076 and1078, which may correspond to the lenses 1042 and 1044 shown in FIGS.2A-4 . The light guide 1070 allows light 1074 from the ambientenvironment to reach the viewer's eye 210. In addition, the light guide1070 functions as folded optics that guides light 1072, emitted by thelight source SLM 1000 and modified by the image SLM 1020, to theviewer's eyes 210. In some embodiments, the reflective instructors 1076and 1078 may be partially-transparent curved specular reflectors.

With continued reference to FIG. 5 , the imaging device 1050 may bedisposed off-axis relative to the gaze direction of the eye 210, e.g.,such that the imaging device 1050 is not in the field of view of the eye210. The imaging device 1050 may be part of an eye imaging assembly 1056comprising a light guide 1054 (e.g., a waveguide) configured to guidelight 1058 from the eye 210 to the imaging device 1050. The light guide1054 may include in-coupling optical elements 1055 configured toin-couple the light 1058 into the light guide 1054. The in-coupled light1058 may be guided within the light guide 1054 by total internalreflection until it exits the light guide 1054 towards the imagingdevice 1050.

In some embodiments, the imaging device 1050 may be configured to imagethe eye using electromagnetic radiation outside of the visible spectrum.For example, the imaging device 1050 may be configured to image the eyeby detecting infrared light. In some embodiments, the imaging device1050 may also include an infrared light emitter configured to illuminatethe eye with infrared light. For example, the imaging device 1050 mayinclude an infrared light emitter which injects light into the lightguide 1054 and this infrared light may be ejected out of the light guide1054 by the optical elements 1055.

FIG. 6 illustrates an example of the display system of FIG. 5 having anoff-axis, mirror based eye imaging device. The illustrated displaysystem is similar to that illustrated in FIG. 5 , except that light 1058from the eye 210 is reflected to the imaging device 1050 using apartially reflective and partially transparent mirror 1057. The mirror1057 may be a specular reflector. In some other embodiments, the mirror1057 may be an off-axis mirror in which the angle of reflection of lightfrom the mirror is different from the angle of incidence of that lighton the mirror. For example, the mirror 1057 may include diffractiveoptical elements having diffractive structures configured (e.g.,oriented and formed) to reflect light from the eye 210 in a direction tobe captured by the imaging device 1050, with the angle of incidence ofthe light from the eye 210 being different from the angle of reflectionof that light from the mirror 1057.

With continued reference to FIG. 6 , in some embodiments the mirror 1057may be disposed on the light guide 1070. As noted above, in someembodiments, the imaging device 1050 may be configured to detectelectromagnetic radiation, e.g., infrared light, outside of the visiblespectrum. In some embodiments, the imaging device 1050 may also includean infrared light emitter to illuminate the eye 210.

In addition to the optical combiner configurations shown in FIGS. 4 and5 , it will be appreciated that the eye tracking and exit pupilalignment system disclosed herein may be utilized in conjunction withvarious other optical combiners. For example, the optical combiner 1040may comprise one or more light guides comprising diffractive opticalelements for in-coupling and out-coupling light encoded with imageinformation. Examples of such light guides include light guides of thelight guide stack 250 (FIG. 14 ) and 660 (FIG. 16 ).

As another example, the optical combiner may be a bird-bath opticalcombiner. In some embodiments, the bird-bath optical combiner mayinclude a beam splitter and a partially-transparent mirror (e.g., apartially-transparent spherical mirror), with the beam splitterdirecting light encoded with image information to the mirror, which thenreflects the light back to the viewer. Both the beam splitter and thepartially-transparent mirror may be partially transparent, therebyallowing light from the ambient environment (the outside world) to reachthe viewer's eyes. Further details regarding bird-bath optical combinersmay be found in US 2015/0346495, published Dec. 3, 2015, the entirety ofwhich is incorporated by reference herein.

[In another example, FIG. 7 illustrates a display system with a foldedrelay mirror combiner. The display system of FIG. 7 is similar to thatof FIG. 6 , except that the relay lens system 1040 comprises foldedmirrors 1077 and 1079 in place of the lens structures 1076 and 1078 ofFIG. 6 . As illustrated, the eye imaging assembly 1056 may comprise amirror 1057 configured to direct light to the imaging device 1050 toimage the eye 210. In some other embodiments, the eye imaging assembly1056 may comprise the light guide 1054 (FIG. 5 ) configured to collectand propagate light to the image capture device 1050.

It will be appreciated that FIGS. 2A-7 illustrate systems for providinglight and image information to a single eye for ease of illustration anddescription. It will also be appreciated that, to provide light andimage information to two eyes of a viewer, a display system may have twoof the illustrated systems, one for each eye.

In addition, in some embodiments, rather than a plurality of lightemitters disposed at different locations, the light source 1000 mayinclude one or more light emitters that can change the apparent locationof light output, thereby mimicking the light output of a light sourcehaving an array of light emitters. For example, the light source maycomprise a linear transfer lens such as a F-theta (F-θ or F-tan θ) lens,a common or shared light emitter, and an actuator to direct the lightemitted by the light emitter along different paths through the F-thetalens. The light exits the light source at different locations throughthe F-theta lens, which focuses the exiting light onto an image plane.Light exiting the F-theta lens at different locations is also disposedat different locations on the image plane, and the image plane may beconsidered to provide a virtual 2D light emitter array. Consequently,the individual regions of the light emitter array, and the locations atwhich light from the linear transfer lens passes through the image planemay both be considered to be the light output locations of the lightsource.

In some embodiments, the actuator may be part of a dual axisgalvanometer comprising a plurality (e.g., a pair) of mirrors that areindependently actuated on different axes to direct light from the lightemitter along the desired path of propagation. In some otherembodiments, the light source may comprise a fiber scanner and theactuator may be an actuator configured to move the fiber of the fiberscanner. The light source may also comprise or be in communication witha processing module which synchronizes the output of light by the lightsource with the location of the mirrors or fiber, and with theintra-pupil image to be displayed. For example, the mirrors or fiber maymove along a known path and the light emitter may be controlled by theprocessing module to emit light when the mirrors or fiber are at aposition corresponding to a desired light output location for a negativeimage, as discussed further herein. Examples of such light sources aredescribed in U.S. application Ser. No. 15/789,895 filed on Oct. 20,2017, the entire disclosure of which is incorporated by referenceherein.

Example Display Systems with Accommodation-Vergence Matching

Advantageously, the displays systems disclosed herein may be configuredto provide a high level of accommodation-vergence matching, which mayprovide various benefits, such as for viewing comfort and long-termwearability. For example, in contrast to conventional stereoscopicdisplays, the eyepiece (e.g., the optical combiner 1040) of the displaysystem may be configured to provide selectively variable amounts ofwavefront divergence, which may provide the desired accommodation cuesto achieve a match with vergence cues provided by displaying slightlydifferent views to each eye of a viewer.

FIG. 8 illustrates a conventional display system for simulatingthree-dimensional imagery for a user. It will be appreciated that auser's eyes are spaced apart and that, when looking at a real object inspace, each eye will have a slightly different view of the object andmay form an image of the object at different locations on the retina ofeach eye. This may be referred to as binocular disparity and may beutilized by the human visual system to provide a perception of depth.Conventional display systems simulate binocular disparity by presentingtwo distinct images 190, 200 with slightly different views of the samevirtual object—one for each eye 210, 220—corresponding to the views ofthe virtual object that would be seen by each eye were the virtualobject a real object at a desired depth. These images provide binocularcues that the user's visual system may interpret to derive a perceptionof depth.

With continued reference to FIG. 8 , the images 190, 200 are spaced fromthe eyes 210, 220 by a distance 230 on a z-axis. The z-axis is parallelto the optical axis of the viewer with their eyes fixated on an objectat optical infinity directly ahead of the viewer. The images 190, 200are flat and at a fixed distance from the eyes 210, 220. Based on theslightly different views of a virtual object in the images presented tothe eyes 210, 220, respectively, the eyes may naturally rotate such thatan image of the object falls on corresponding points on the retinas ofeach of the eyes, to maintain single binocular vision. This rotation maycause the lines of sight of each of the eyes 210, 220 to converge onto apoint in space at which the virtual object is perceived to be present.As a result, providing three-dimensional imagery conventionally involvesproviding binocular cues that may manipulate the vergence of the user'seyes 210, 220, and that the human visual system interprets to provide aperception of depth.

Generating a realistic and comfortable perception of depth ischallenging, however. It will be appreciated that light from objects atdifferent distances from the eyes have wavefronts with different amountsof divergence. FIGS. 9A-9C illustrate relationships between distance andthe divergence of light rays. The distance between the object and theeye 210 is represented by, in order of decreasing distance, R1, R2, andR3. As shown in FIGS. 9A-9C, the light rays become more divergent asdistance to the object decreases. Conversely, as distance increases, thelight rays become more collimated. Stated another way, it may be saidthat the light field produced by a point (the object or a part of theobject) has a spherical wavefront curvature, which is a function of howfar away the point is from the eye of the user. The curvature increaseswith decreasing distance between the object and the eye 210. While onlya single eye 210 is illustrated for clarity of illustration in FIGS.9A-9C and other figures herein, the discussions regarding eye 210 may beapplied to both eyes 210 and 220 of a viewer.

With continued reference to FIGS. 9A-9C, light from an object that theviewer's eyes are fixated on may have different degrees of wavefrontdivergence. Due to the different amounts of wavefront divergence, thelight may be focused differently by the lens of the eye, which in turnmay require the lens to assume different shapes to form a focused imageon the retina of the eye. Where a focused image is not formed on theretina, the resulting retinal blur acts as a cue to accommodation thatcauses a change in the shape of the lens of the eye until a focusedimage is formed on the retina. For example, the cue to accommodation maytrigger the ciliary muscles surrounding the lens of the eye to relax orcontract, thereby modulating the force applied to the suspensoryligaments holding the lens, thus causing the shape of the lens of theeye to change until retinal blur of an object of fixation is eliminatedor minimized, thereby forming a focused image of the object of fixationon the retina (e.g., fovea) of the eye. The process by which the lens ofthe eye changes shape may be referred to as accommodation, and the shapeof the lens of the eye required to form a focused image of the object offixation on the retina (e.g., fovea) of the eye may be referred to as anaccommodative state.

With reference now to FIG. 10 , a representation of theaccommodation-vergence response of the human visual system isillustrated. The movement of the eyes to fixate on an object causes theeyes to receive light from the object, with the light forming an imageon each of the retinas of the eyes. The presence of retinal blur in theimage formed on the retina may provide a cue to accommodation, and therelative locations of the image on the retinas may provide a cue tovergence. The cue to accommodation causes accommodation to occur,resulting in the lenses of the eyes each assuming a particularaccommodative state that forms a focused image of the object on theretina (e.g., fovea) of the eye. On the other hand, the cue to vergencecauses vergence movements (rotation of the eyes) to occur such that theimages formed on each retina of each eye are at corresponding retinalpoints that maintain single binocular vision. In these positions, theeyes may be said to have assumed a particular vergence state. Withcontinued reference to FIG. 10 , accommodation may be understood to bethe process by which the eye achieves a particular accommodative state,and vergence may be understood to be the process by which the eyeachieves a particular vergence state. As indicated in FIG. 10 , theaccommodative and vergence states of the eyes may change if the userfixates on another object. For example, the accommodated state maychange if the user fixates on a new object at a different depth on thez-axis.

Without being limited by theory, it is believed that viewers of anobject may perceive the object as being “three-dimensional” due to acombination of vergence and accommodation. As noted above, vergencemovements (e.g., rotation of the eyes so that the pupils move toward oraway from each other to converge the lines of sight of the eyes tofixate upon an object) of the two eyes relative to each other areclosely associated with accommodation of the lenses of the eyes. Undernormal conditions, changing the shapes of the lenses of the eyes tochange focus from one object to another object at a different distancewill automatically cause a matching change in vergence to the samedistance, under a relationship known as the “accommodation-vergencereflex.” Likewise, a change in vergence will trigger a matching changein lens shape under normal conditions.

With reference now to FIG. 11 , examples of different accommodative andvergence states of the eyes are illustrated. The pair of eyes 222 a isfixated on an object at optical infinity, while the pair eyes 222 b arefixated on an object 221 at less than optical infinity. Notably, thevergence states of each pair of eyes is different, with the pair of eyes222 a directed straight ahead, while the pair of eyes 222 converge onthe object 221. The accommodative states of the eyes forming each pairof eyes 222 a and 222 b are also different, as represented by thedifferent shapes of the lenses 210 a, 220 a.

Undesirably, many users of conventional “3-D” display systems find suchconventional systems to be uncomfortable or may not perceive a sense ofdepth at all due to a mismatch between accommodative and vergence statesin these displays. As noted above, many stereoscopic or “3-D” displaysystems display a scene by providing slightly different images to eacheye. Such systems are uncomfortable for many viewers, since they, amongother things, simply provide different presentations of a scene andcause changes in the vergence states of the eyes, but without acorresponding change in the accommodative states of those eyes. Rather,the images are shown by a display at a fixed distance from the eyes,such that the eyes view all the image information at a singleaccommodative state. Such an arrangement works against the“accommodation-vergence reflex” by causing changes in the vergence statewithout a matching change in the accommodative state. This mismatch isbelieved to cause viewer discomfort. Display systems that provide abetter match between accommodation and vergence may form more realisticand comfortable simulations of three-dimensional imagery.

Without being limited by theory, it is believed that the human eyetypically may interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited numbers of depthplanes. In some embodiments, the different presentations may provideboth cues to vergence and matching cues to accommodation, therebyproviding physiologically correct accommodation-vergence matching.

With continued reference to FIG. 11 , two depth planes 240,corresponding to different distances in space from the eyes 210, 220,are illustrated. For a given depth plane 240, vergence cues may beprovided by the displaying of images of appropriately differentperspectives for each eye 210, 220. In addition, for a given depth plane240, light forming the images provided to each eye 210, 220 may have awavefront divergence corresponding to a light field produced by a pointat the distance of that depth plane 240.

In the illustrated embodiment, the distance, along the z-axis, of thedepth plane 240 containing the point 221 is 1 m. As used herein,distances or depths along the z-axis may be measured with a zero-pointlocated at the pupils of the user's eyes. Thus, a depth plane 240located at a depth of 1 m corresponds to a distance of 1 m away from thepupils of the user's eyes, on the optical axis of those eyes with theeyes directed towards optical infinity. As an approximation, the depthor distance along the z-axis may be measured from the display in frontof the user's eyes (e.g., from the surface of a light guide), plus avalue for the distance between the device and the pupils of the user'seyes. That value may be called the eye relief and corresponds to thedistance between the pupil of the user's eye and the display worn by theuser in front of the eye. In practice, the value for the eye relief maybe a normalized value used generally for all viewers. For example, theeye relief may be assumed to be 20 mm and a depth plane that is at adepth of 1 m may be at a distance of 980 mm in front of the display.

With reference now to FIGS. 12A and 12B, examples of matchedaccommodation-vergence distances and mismatched accommodation-vergencedistances are illustrated, respectively. As illustrated in FIG. 12A, thedisplay system may provide images of a virtual object to each eye 210,220. The images may cause the eyes 210, 220 to assume a vergence statein which the eyes converge on a point 15 on a depth plane 240. Inaddition, the images may be formed by a light having a wavefrontcurvature corresponding to real objects at that depth plane 240. As aresult, the eyes 210, 220 assume an accommodative state in which theimages are in focus on the retinas of those eyes. Thus, the user mayperceive the virtual object as being at the point 15 on the depth plane240.

It will be appreciated that each of the accommodative and vergencestates of the eyes 210, 220 are associated with a particular distance onthe z-axis. For example, an object at a particular distance from theeyes 210, 220 causes those eyes to assume particular accommodativestates based upon the distances of the object. The distance associatedwith a particular accommodative state may be referred to as theaccommodation distance, A_(d). Similarly, there are particular vergencedistances, V_(d), associated with the eyes in particular vergencestates, or positions relative to one another. Where the accommodationdistance and the vergence distance match, the relationship betweenaccommodation and vergence may be said to be physiologically correct.This is considered to be the most comfortable scenario for a viewer.

In stereoscopic displays, however, the accommodation distance and thevergence distance may not always match. For example, as illustrated inFIG. 12B, images displayed to the eyes 210, 220 may be displayed withwavefront divergence corresponding to depth plane 240, and the eyes 210,220 may assume a particular accommodative state in which the points 15a, 15 b on that depth plane are in focus. However, the images displayedto the eyes 210, 220 may provide cues for vergence that cause the eyes210, 220 to converge on a point 15 that is not located on the depthplane 240. As a result, the accommodation distance corresponds to thedistance from the pupils of the eyes 210, 220 to the depth plane 240,while the vergence distance corresponds to the larger distance from thepupils of the eyes 210, 220 to the point 15, in some embodiments. Theaccommodation distance is different from the vergence distance.Consequently, there is an accommodation-vergence mismatch. Such amismatch is considered undesirable and may cause discomfort in the user.It will be appreciated that the mismatch corresponds to distance (e.g.,V_(d)−A_(d)) and may be characterized using diopters.

In some embodiments, it will be appreciated that a reference point otherthan pupils of the eyes 210, 220 may be utilized for determiningdistance for determining accommodation-vergence mismatch, so long as thesame reference point is utilized for the accommodation distance and thevergence distance. For example, the distances could be measured from thecornea to the depth plane, from the retina to the depth plane, from theeyepiece (e.g., a light guide of the display device) to the depth plane,and so on.

Without being limited by theory, it is believed that users may stillperceive accommodation-vergence mismatches of up to about 0.25 diopter,up to about 0.33 diopter, and up to about 0.5 diopter as beingphysiologically correct, without the mismatch itself causing significantdiscomfort. In some embodiments, display systems disclosed herein (e.g.,the display system 250, FIG. 14 ) present images to the viewer havingaccommodation-vergence mismatch of about 0.5 diopter or less. In someother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.33 diopter or less. In yetother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.25 diopter or less, includingabout 0.1 diopter or less.

FIG. 13 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence. The displaysystem includes an eyepiece 1040 that is configured to receive light 770that is encoded with image information, and to output that light to theuser's eye 210. In some embodiments, the eyepiece 1040 may include alight guide 270 (e.g., a waveguide). The light guide 270 may output thelight 650 with a defined amount of wavefront divergence corresponding tothe wavefront divergence of a light field produced by a point on adesired depth plane 240. In some embodiments, the same amount ofwavefront divergence is provided for all objects presented on that depthplane. In addition, it will be illustrated that the other eye of theuser may be provided with image information from a similar light guide.

In some embodiments, a single light guide may be configured to outputlight with a set amount of wavefront divergence corresponding to asingle or limited number of depth planes and/or the light guide may beconfigured to output light of a limited range of wavelengths.Consequently, in some embodiments, the eyepiece 1040 may include aplurality or stack of light guides may be utilized to provide differentamounts of wavefront divergence for different depth planes and/or tooutput light of different ranges of wavelengths. As used herein, it willbe appreciated at a depth plane may follow the contours of a flat or acurved surface. In some embodiments, advantageously for simplicity, thedepth planes may follow the contours of flat surfaces.

FIG. 14 illustrates an example of a light guide stack for outputtingimage information to a user. A display system 250 includes an eyepiece1040 having a stack of light guides, or stacked light guide assembly,260 that may be utilized to provide three-dimensional perception to theeye/brain using a plurality of light guides 270, 280, 290, 300, 310. Itwill be appreciated that the display system 250 may be considered alight field display in some embodiments.

In some embodiments, the display system 250 may be configured to providesubstantially continuous cues to vergence and multiple discrete cues toaccommodation. The cues to vergence may be provided by displayingdifferent images to each of the eyes of the user, and the cues toaccommodation may be provided by outputting the light that forms theimages with selectable discrete amounts of wavefront divergence. Statedanother way, the display system 250 may be configured to output lightwith variable levels of wavefront divergence. In some embodiments, eachdiscrete level of wavefront divergence corresponds to a particular depthplane and may be provided by a particular one of the light guides 270,280, 290, 300, 310.

With continued reference to FIG. 14 , the light guide assembly 260 mayalso include a plurality of features 320, 330, 340, 350 between thelight guides. In some embodiments, the features 320, 330, 340, 350 maybe one or more lenses. In some embodiments, the lenses 320, 330, 340,350 may correspond to the lens 1046 (FIG. 2A). The light guides 270,280, 290, 300, 310 and/or the plurality of lenses 320, 330, 340, 350 maybe configured to send image information to the eye with various levelsof wavefront curvature or light ray divergence. Each light guide levelmay be associated with a particular depth plane and may be configured tooutput image information corresponding to that depth plane.

In some embodiments, light is injected into the light guides 270, 280,290, 300, 310 by an image injection system 520, which comprises a lightmodule 530, which may include a light emitter, such as a light emittingdiode (LED). The light from the light module 530 may be directed to andmodified by a light modulator 540, e.g., a spatial light modulator, viaa beam splitter 550. It will be appreciated that the light module 530may correspond to the light source 1000 and the light modulator 540 maycorrespond to the image SLM 1020 (FIGS. 2A-7 ).

The light modulator 540 may be configured to change the perceivedintensity of the light injected into the light guides 270, 280, 290,300, 310 to encode the light with image information. Examples of spatiallight modulators include liquid crystal displays (LCD) including liquidcrystal on silicon (LCOS) displays. In some embodiments, the imageinjection system 520 may be a scanning fiber display comprising one ormore scanning fibers configured to project light in various patterns(e.g., raster scan, spiral scan, Lissajous patterns, etc.) into one ormore light guides 270, 280, 290, 300, 310 and ultimately to the eye 210of the viewer.

With continued reference to FIG. 14 , a controller 560 controls theoperation of one or more of the stacked light guide assembly 260, thelight source 530, and the light modulator 540. In some embodiments, thecontroller 560 is part of the local data processing module 140. Thecontroller 560 includes programming (e.g., instructions in anon-transitory medium) that regulates the timing and provision of imageinformation to the light guides 270, 280, 290, 300, 310 according to,e.g., any of the various schemes disclosed herein. In some embodiments,the controller may be a single integral device, or a distributed systemconnected by wired or wireless communication channels. The controller560 may be part of the processing modules 140 or 150 (FIG. 17 ) in someembodiments.

With continued reference to FIG. 14 , the light guides 270, 280, 290,300, 310 may be configured to propagate light within each respectivelight guide by total internal reflection (TIR). The light guides 270,280, 290, 300, 310 may each be planar or have another shape (e.g.,curved), with major top and bottom surfaces, and edges extending betweenthose major top and bottom surfaces. In the illustrated configuration,the light guides 270, 280, 290, 300, 310 may each include out-couplingoptical elements 570, 580, 590, 600, 610 that are configured to extractlight out of a light guide by redirecting the light, propagating withineach respective light guide, out of the light guide to output imageinformation to the eye 210. Extracted light may also be referred to asout-coupled light and the out-coupling optical elements light may alsobe referred to light extracting optical elements. The out-couplingoptical elements 570, 580, 590, 600, 610 may, for example, be gratings,including diffractive optical features, as discussed further herein.While illustrated disposed at the bottom major surfaces of the lightguides 270, 280, 290, 300, 310, for ease of description and drawingclarity, in some embodiments, the out-coupling optical elements 570,580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of the lightguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the light guides 270, 280, 290, 300, 310. In someother embodiments, the light guides 270, 280, 290, 300, 310 may be amonolithic piece of material and the out-coupling optical elements 570,580, 590, 600, 610 may be formed on a surface and/or in the interior ofthat piece of material. In some embodiments, the out-coupling opticalelements 570, 580, 590, 600, 610 may correspond to the lens structures1078, 1079 (FIGS. 5-7 ).

With continued reference to FIG. 14 , as discussed herein, each lightguide 270, 280, 290, 300, 310 is configured to output light to form animage corresponding to a particular depth plane. For example, the lightguide 270 nearest the eye may be configured to deliver collimated lightto the eye 210. The collimated light may be representative of theoptical infinity focal plane. The next light guide up 280 may beconfigured to send out collimated light which passes through the firstlens 350 (e.g., a negative lens) before it may reach the eye 210; suchfirst lens 350 may be configured to create a slight convex wavefrontcurvature so that the eye/brain interprets light coming from that nextlight guide up 280 as coming from a first focal plane closer inwardtoward the eye 210 from optical infinity. Similarly, the third up lightguide 290 passes its output light through both the first 350 and second340 lenses before reaching the eye 210; the combined optical power ofthe first 350 and second 340 lenses may be configured to create anotherincremental amount of wavefront curvature so that the eye/braininterprets light coming from the third light guide 290 as coming from asecond focal plane that is even closer inward toward the person fromoptical infinity than was light from the next light guide up 280.

The other light guide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest light guide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked light guide assembly 260, a compensating lens layer 620may be disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are available lightguide/lens pairings. Both the out-coupling optical elements of the lightguides and the focusing aspects of the lenses may be static (i.e., notdynamic or electro-active). In some alternative embodiments, either orboth may be dynamic using electro-active features.

In some embodiments, two or more of the light guides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplelight guides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the light guides270, 280, 290, 300, 310 may be configured to output images set to thesame plurality of depth planes, with one set for each depth plane. Thismay provide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 14 , the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective light guides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the light guide. As a result, light guides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, as discussed herein, an eye imaging assembly 1056(e.g., a digital camera, including visible light and infrared lightcameras) may be provided to capture images of the eye 210. As usedherein, a camera may be any image capture device. In some embodiments,the eye imaging assembly 1056 may include an image capture device and alight source to project light (e.g., infrared light) to the eye, whichmay then be reflected by the eye and detected by the image capturedevice. In some embodiments, the eye imaging assembly 1056 may beattached to the frame 80 (FIG. 17 ) and may be in electricalcommunication with the processing modules 140 and/or 150, which mayprocess image information from the eye imaging assembly 1056. In someembodiments, one eye imaging assembly 1056 may be utilized for each eye,to separately monitor each eye.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 15 illustrates an example of a stackedlight guide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated light guide and, consequently, each depth plane mayhave multiple light guides associated with it. In such embodiments, eachbox in the figures including the letters G, R, or B may be understood torepresent an individual light guide, and three light guides may beprovided per depth plane where three component color images are providedper depth plane. While the light guides associated with each depth planeare shown adjacent to one another in this drawing for ease ofdescription, it will be appreciated that, in a physical device, thelight guides may all be arranged in a stack with one light guide perlevel. In some other embodiments, multiple component colors may beoutputted by the same light guide, such that, e.g., only a single lightguide may be provided per depth plane.

With continued reference to FIG. 15 , in some embodiments, G is thecolor green, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 530 (FIG. 14 ) may be configuredto emit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the light guides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 16 , in some embodiments, light impinging ona light guide may be redirected to in-couple that light into the lightguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding light guide. FIG. 16illustrates a cross-sectional side view of an example of a plurality orset 660 of stacked light guides that each includes an in-couplingoptical element. The light guides may each be configured to output lightof one or more different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 14 ) and the illustrated light guides of the stack660 may correspond to part of the plurality of light guides 270, 280,290, 300, 310.

The illustrated set 660 of stacked light guides includes light guides670, 680, and 690. Each light guide includes an associated in-couplingoptical element (which may also be referred to as a light input area onthe light guide), with, e.g., in-coupling optical element 700 disposedon a major surface (e.g., an upper major surface) of light guide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of light guide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) of lightguide 690. In some embodiments, one or more of the in-coupling opticalelements 700, 710, 720 may be disposed on the bottom major surface ofthe respective light guide 670, 680, 690 (particularly where the one ormore in-coupling optical elements are reflective, deflecting opticalelements). As illustrated, the in-coupling optical elements 700, 710,720 may be disposed on the upper major surface of their respective lightguide 670, 680, 690 (or the top of the next lower light guide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective light guide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective light guide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respective lightguide 670, 680, 690 in some embodiments. The in-coupling opticalelements 700, 710, 720 may correspond to the lens structures 1076, 1077(FIGS. 5-7 ).

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another. In some embodiments, each in-couplingoptical element may be offset such that it receives light without thatlight passing through another in-coupling optical element. For example,each in-coupling optical element 700, 710, 720 may be configured toreceive light from a different SLM or a different part of an image SLM,and may be separated (e.g., laterally spaced apart) from otherin-coupling optical elements 700, 710, 720 such that it substantiallydoes not receive light incident on other ones of the in-coupling opticalelements 700, 710, 720. In addition, each in-coupling optical element700, 710, 720 may have a dedicated associated SLM to display negativeimages of the viewer's eye, or may display the negative images atdifferent parts of the light source SLM 1000 corresponding to individualones of the in-coupling optical elements 700, 710, 720. In someembodiments, each in-coupling optical element 700, 710, 720 may havededicated associated optical elements, including dedicated associatedlight source condensing/collimating optics and relay optics in the pathof the light from the displayed negative image to the correspondingin-coupling optical element 700, 710, or 720.

The light guides 670, 680, 690 may be spaced apart and separated by,e.g., gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate light guides 670 and 680; andlayer 760 b may separate light guides 680 and 690. In some embodiments,the layers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of light guides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the light guides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe light guides 670, 680, 690 (e.g., TIR between the top and bottommajor surfaces of each light guide). In some embodiments, the layers 760a, 760 b are formed of air. While not illustrated, it will beappreciated that the top and bottom of the illustrated set 660 of lightguides may include immediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the light guides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the light guides 670,680, 690 may be different between one or more light guides, and/or thematerial forming the layers 760 a, 760 b may be different, while stillholding to the various refractive index relationships noted above.

With continued reference to FIG. 16 , light rays 770, 780, 790 areincident on the set 660 of light guides. In some embodiments, the lightrays 770, 780, 790 have different properties, e.g., differentwavelengths or different ranges of wavelengths, which may correspond todifferent colors. The in-coupling optical elements 700, 710, 720 eachdeflect the incident light such that the light propagates through arespective one of the light guides 670, 680, 690 by TIR. In someembodiments, the in-coupling optical elements 700, 710, 720 eachselectively deflect one or more particular wavelengths of light, whiletransmitting other wavelengths to an underlying light guide andassociated in-coupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 16 , the deflected light rays 770, 780,790 are deflected so that they propagate through a corresponding lightguide 670, 680, 690; that is, the in-coupling optical elements 700, 710,720 of each light guide deflects light into that corresponding lightguide 670, 680, 690 to in-couple light into that corresponding lightguide. The light rays 770, 780, 790 are deflected at angles that causethe light to propagate through the respective light guide 670, 680, 690by TIR. The light rays 770, 780, 790 then impinge on the out-couplingoptical elements 800, 810, 820, respectively. In some embodiments, theout-coupling optical elements 800, 810, 820 may correspond to the lensstructures 1078, 1079 (FIGS. 5-7 ).

Accordingly, with reference to FIG. 16 , in some embodiments, the set660 of light guides includes light guides 670, 680, 690; in-couplingoptical elements 700, 710, 720; and out-coupling optical elements 800,810, 820 for each component color. The light guides 670, 680, 690 may bestacked with an air gap/cladding layer between each one. The in-couplingoptical elements 700, 710, 720 redirect or deflect incident light (withdifferent in-coupling optical elements receiving light of differentwavelengths) into its light guide. The light then propagates at an anglewhich will result in TIR within the respective light guide 670, 680,690. In the example shown, light ray 770 (e.g., blue light) is deflectedby the first in-coupling optical element 700, and then continues tobounce down the light guide and then interact with the out-couplingoptical element 800. The light rays 780 and 790 (e.g., green and redlight, respectively) will pass through the light guide 670, with lightray 780 impinging on and being deflected by in-coupling optical element710. The light ray 780 then bounces down the light guide 680 via TIR,proceeding on to the out-coupling optical element 810. Finally, lightray 790 (e.g., red light) passes through the light guide 690 to impingeon the light in-coupling optical elements 720 of the light guide 690.The light in-coupling optical elements 720 deflect the light ray 790such that the light ray propagates to the out-coupling optical element820 by TIR. The out-coupling optical element 820 then finallyout-couples the light ray 790 to the viewer, who may also receive theout-coupled light from the other light guides 670, 680.

FIG. 17 illustrates an example of wearable display system 60 into whichthe various light guides and related systems disclosed herein may beintegrated. In some embodiments, the display system 60 is the system 250of FIG. 14 , with FIG. 14 schematically showing some parts of thatsystem 60 in greater detail. For example, the light guide assembly 260of FIG. 14 may be part of the display 70.

With continued reference to FIG. 17 , the display system 60 includes adisplay 70, and various mechanical and electronic modules and systems tosupport the functioning of that display 70. The display 70 may becoupled to a frame 80, which is wearable by a display system user orviewer 90 and which is configured to position the display 70 in front ofthe eyes of the user 90. The display 70 may be considered eyewear insome embodiments. In some embodiments, a speaker 100 is coupled to theframe 80 and configured to be positioned adjacent the ear canal of theuser 90 (in some embodiments, another speaker, not shown, may optionallybe positioned adjacent the other ear canal of the user to providestereo/shapeable sound control). The display system 60 may also includeone or more microphones 110 or other devices to detect sound. In someembodiments, the microphone is configured to allow the user to provideinputs or commands to the system 60 (e.g., the selection of voice menucommands, natural language questions, etc.), and/or may allow audiocommunication with other persons (e.g., with other users of similardisplay systems. The microphone may further be configured as aperipheral sensor to collect audio data (e.g., sounds from the userand/or environment). In some embodiments, the display system 60 mayfurther include one or more outwardly-directed environmental sensors 112configured to detect objects, stimuli, people, animals, locations, orother aspects of the world around the user. For example, environmentalsensors 112 may include one or more cameras, which may be located, e.g.,facing outward so as to capture images similar to at least a portion ofan ordinary field of view of the user 90. In some embodiments, thedisplay system may also include a peripheral sensor 120 a, which may beseparate from the frame 80 and attached to the body of the user 90(e.g., on the head, torso, an extremity, etc. of the user 90). Theperipheral sensor 120 a may be configured to acquire data characterizinga physiological state of the user 90 in some embodiments. For example,the sensor 120 a may be an electrode.

With continued reference to FIG. 17 , the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. Optionally, the local processor and data module 140 may includeone or more central processing units (CPUs), graphics processing units(GPUs), dedicated processing hardware, and so on. The data may includedata a) captured from sensors (which may be, e.g., operatively coupledto the frame 80 or otherwise attached to the user 90), such as imagecapture devices (such as cameras), microphones, inertial measurementunits, accelerometers, compasses, GPS units, radio devices, gyros,and/or other sensors disclosed herein; and/or b) acquired and/orprocessed using remote processing module 150 and/or remote datarepository 160 (including data relating to virtual content), possiblyfor passage to the display 70 after such processing or retrieval. Thelocal processing and data module 140 may be operatively coupled bycommunication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 17 , in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information, for instanceincluding one or more central processing units (CPUs), graphicsprocessing units (GPUs), dedicated processing hardware, and so on. Insome embodiments, the remote data repository 160 may comprise a digitaldata storage facility, which may be available through the internet orother networking configuration in a “cloud” resource configuration. Insome embodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating augmented reality content, to the local processing and datamodule 140 and/or the remote processing module 150. In some embodiments,all data is stored and all computations are performed in the localprocessing and data module, allowing fully autonomous use from a remotemodule. Optionally, an outside system (e.g., a system of one or moreprocessors, one or more computers) that includes CPUs, GPUs, and so on,may perform at least a portion of processing (e.g., generating imageinformation, processing data) and provide information to, and receiveinformation from, modules 140, 150, 160, for instance via wireless orwired connections.

Computer Vision to Detect Objects or Features in Captured Images

As discussed above, the display system may be configured to detectobjects or features in captured images. In some embodiments, objects orfeatures present in the images may be detected using computer visiontechniques. For example, the display system may be configured to performimage analysis on the captured images to determine the presence ofparticular objects or features in those images. The display system mayanalyze the captured images to determine the presence and contours ofthe ocular pupil in some embodiments.

One or more computer vision algorithms may be used to perform thesetasks. Non-limiting examples of computer vision algorithms include:Scale-invariant feature transform (SIFT), speeded up robust features(SURF), oriented FAST and rotated BRIEF (ORB), binary robust invariantscalable keypoints (BRISK), fast retina keypoint (FREAK), Viola-Jonesalgorithm, Eigenfaces approach, Lucas-Kanade algorithm, Horn-Schunkalgorithm, Mean-shift algorithm, visual simultaneous location andmapping (vSLAM) techniques, a sequential Bayesian estimator (e.g.,Kalman filter, extended Kalman filter, etc.), bundle adjustment,Adaptive thresholding (and other thresholding techniques), IterativeClosest Point (ICP), Semi Global Matching (SGM), Semi Global BlockMatching (SGBM), Feature Point Histograms, various machine learningalgorithms (such as e.g., support vector machine, k-nearest neighborsalgorithm, Naive Bayes, neural network (including convolutional or deepneural networks), or other supervised/unsupervised models, etc.), and soforth.

Machine Learning

A variety of machine learning algorithms may be used to learn toidentify the presence, shape, location, etc. of the ocular pupil. Oncetrained, the machine learning algorithms may be stored by the displaysystem. Some examples of machine learning algorithms may includesupervised or non-supervised machine learning algorithms, includingregression algorithms (such as, for example, Ordinary Least SquaresRegression), instance-based algorithms (such as, for example, LearningVector Quantization), decision tree algorithms (such as, for example,classification and regression trees), Bayesian algorithms (such as, forexample, Naive Bayes), clustering algorithms (such as, for example,k-means clustering), association rule learning algorithms (such as, forexample, a-priori algorithms), artificial neural network algorithms(such as, for example, Perceptron), deep learning algorithms (such as,for example, Deep Boltzmann Machine, or deep neural network),dimensionality reduction algorithms (such as, for example, PrincipalComponent Analysis), ensemble algorithms (such as, for example, StackedGeneralization), and/or other machine learning algorithms. In someembodiments, individual models may be customized for individual datasets. For example, the display system may generate or store a basemodel. The base model may be used as a starting point to generateadditional models specific to a data type (e.g., a particular user), adata set (e.g., a set of additional images obtained), conditionalsituations, or other variations. In some embodiments, the display systemmay be configured to utilize a plurality of techniques to generatemodels for analysis of the aggregated data. Other techniques may includeusing pre-defined thresholds or data values.

The criteria for detecting an object or feature may include one or morethreshold conditions. If the analysis of the captured image indicatesthat a threshold condition is passed, the display system may provide asignal indicating the detection the presence of the object in the image.The threshold condition may involve a quantitative and/or qualitativemeasure. For example, the threshold condition may include a score or apercentage associated with the likelihood of the object being present inthe image. The display system may compare the score calculated from thecaptured image with the threshold score. If the score is higher than thethreshold level, the display system may detect the presence of theobject or feature. In some other embodiments, the display system maysignal the absence of the object in the image if the score is lower thanthe threshold.

It will be appreciated that each of the processes, methods, andalgorithms described herein and/or depicted in the figures may beembodied in, and fully or partially automated by, code modules executedby one or more physical computing systems, hardware computer processors,application-specific circuitry, and/or electronic hardware configured toexecute specific and particular computer instructions. For example,computing systems may include general purpose computers (e.g., servers)programmed with specific computer instructions or special purposecomputers, special purpose circuitry, and so forth. A code module may becompiled and linked into an executable program, installed in a dynamiclink library, or may be written in an interpreted programming language.In some embodiments, particular operations and methods may be performedby circuitry that is specific to a given function.

Further, certain embodiments of the functionality of the presentdisclosure are sufficiently mathematically, computationally, ortechnically complex that application-specific hardware or one or morephysical computing devices (utilizing appropriate specialized executableinstructions) may be necessary to perform the functionality, forexample, due to the volume or complexity of the calculations involved orto provide results substantially in real-time. For example, a video mayinclude many frames, with each frame having millions of pixels, andspecifically programmed computer hardware is necessary to process thevideo data to provide a desired image processing task or application ina commercially reasonable amount of time.

Code modules or any type of data may be stored on any type ofnon-transitory computer-readable medium, such as physical computerstorage including hard drives, solid state memory, random access memory(RAM), read only memory (ROM), optical disc, volatile or non-volatilestorage, combinations of the same and/or the like. In some embodiments,the non-transitory computer-readable medium may be part of one or moreof the local processing and data module (140), the remote processingmodule (150), and remote data repository (160). The methods and modules(or data) may also be transmitted as generated data signals (e.g., aspart of a carrier wave or other analog or digital propagated signal) ona variety of computer-readable transmission mediums, includingwireless-based and wired/cable-based mediums, and may take a variety offorms (e.g., as part of a single or multiplexed analog signal, or asmultiple discrete digital packets or frames). The results of thedisclosed processes or process steps may be stored, persistently orotherwise, in any type of non-transitory, tangible computer storage ormay be communicated via a computer-readable transmission medium.

Any processes, blocks, states, steps, or functionalities in flowdiagrams described herein and/or depicted in the attached figures shouldbe understood as potentially representing code modules, segments, orportions of code which include one or more executable instructions forimplementing specific functions (e.g., logical or arithmetical) or stepsin the process. The various processes, blocks, states, steps, orfunctionalities may be combined, rearranged, added to, deleted from,modified, or otherwise changed from the illustrative examples providedherein. In some embodiments, additional or different computing systemsor code modules may perform some or all of the functionalities describedherein. The methods and processes described herein are also not limitedto any particular sequence, and the blocks, steps, or states relatingthereto may be performed in other sequences that are appropriate, forexample, in serial, in parallel, or in some other manner. Tasks orevents may be added to or removed from the disclosed exampleembodiments. Moreover, the separation of various system components inthe embodiments described herein is for illustrative purposes and shouldnot be understood as requiring such separation in all embodiments. Itshould be understood that the described program components, methods, andsystems may generally be integrated together in a single computerproduct or packaged into multiple computer products.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense.

Indeed, it will be appreciated that the systems and methods of thedisclosure each have several innovative aspects, no single one of whichis solely responsible or required for the desirable attributes disclosedherein. The various features and processes described above may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure.

Certain features that are described in this specification in the contextof separate embodiments also may be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment also may be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination may in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination. No single feature orgroup of features is necessary or indispensable to each and everyembodiment.

It will be appreciated that conditional language used herein, such as,among others, “can,” “could,” “might,” “may,” “e.g.,” and the like,unless specifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/or stepsare included or are to be performed in any particular embodiment. Theterms “comprising,” “including,” “having,” and the like are synonymousand are used inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list. Inaddition, the articles “a,” “an,” and “the” as used in this applicationand the appended claims are to be construed to mean “one or more” or “atleast one” unless specified otherwise. Similarly, while operations maybe depicted in the drawings in a particular order, it is to berecognized that such operations need not be performed in the particularorder shown or in sequential order, or that all illustrated operationsbe performed, to achieve desirable results. Further, the drawings mayschematically depict one more example processes in the form of aflowchart. However, other operations that are not depicted may beincorporated in the example methods and processes that are schematicallyillustrated. For example, one or more additional operations may beperformed before, after, simultaneously, or between any of theillustrated operations. Additionally, the operations may be rearrangedor reordered in other embodiments. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the embodiments describedabove should not be understood as requiring such separation in allembodiments, and it should be understood that the described programcomponents and systems may generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other embodiments are within the scope of the followingclaims. In some cases, the actions recited in the claims may beperformed in a different order and still achieve desirable results.

Accordingly, the claims are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

What is claimed is:
 1. A head-mounted display system comprising: an eyeimaging device configured to capture images of an eye of a user; a lightsource configured to emit light to form a negative image of the eye; anda spatial light modulator configured to display image content to theuser by encoding image information in light propagating from thenegative image of the eye.
 2. The display system of claim 1, wherein thedisplay system is configured to threshold the captured images of the eyeto convert a captured image to a corresponding negative image.
 3. Thedisplay system of claim 1, wherein the light source is an other spatiallight modulator.
 4. The display system of claim 3, wherein the otherspatial light modulator is an emissive spatial light modulator.
 5. Thedisplay system of claim 4, wherein the emissive spatial light modulatoris an LED array.
 6. The display system of claim 4, wherein the emissivespatial light modulator comprises an array of binary light emitters eachhaving an on state and an off state.
 7. The display system of claim 1,wherein the eye imaging device comprises a camera.
 8. The display systemof claim 7, wherein the eye imaging device comprises a waveguideconfigured to receive light from the eye, and propagate the light bytotal internal reflection through the waveguide and to the camera. 9.The display system of claim 8, wherein the waveguide is in a path oflight encoded with the image information, and wherein the waveguide istransmissive to the light encoded with the image information.
 10. Thedisplay system of claim 7, wherein the eye imaging device comprises amirror configured to reflect light from the eye to the camera.
 11. Thedisplay system of claim 1, further comprising: light source opticsconfigured to collimate light propagating from the light source to thespatial light modulator; light source relay optics configured to receivelight from the spatial light modulator and to form an image of the lightsource; and pupil relay optics configured to receive light from thelight source relay optics and to provide simultaneous images of thelight source and spatial light modulator to the eye.
 12. The displaysystem of claim 1, further comprising a light guide configured to directlight from the spatial light modulator towards an eye of the user. 13.The display system of claim 12, wherein the light guide has opticalpower and is configured to output light with a divergent wavefront. 14.The display system of claim 13, further comprising a plurality of thelight guides, wherein at least some of the plurality of light guideshave different optical power from others of the plurality of lightguides.
 15. The display system of claim 1, further comprising a frameconfigured to mount on a head of the user, wherein at least a lightcapturing portion of the eye imaging device is attached to the frame,and wherein the spatial light modulator is attached to the frame.